300 



GENERAL ORNITHOLOGY 



sions of the lower part of the tube occur in many sea-ducks and 

 mergansers {Fuliguliiue, Mergince), and some other birds ; several 

 lower rings of the trachea being enormously enlarged and welded 

 together into a great bony and membranous box, of wholly irregular, 

 unsymmetrical contour. Such a structure, represented in Figs. 3 

 and 98, is termed a tracheal tympanum, or labyrinth. It is not a 

 part of the voice -organ proper, but may act as a reverberatory 

 chamber to increase the volume of the sound, without however 

 modulating it. Being chiefly developed in the male, it is a kind of 

 secondary sexual organ. The vagaries of the windpipe are still 

 more remarkable. Very generally, in cranes and swans, the trachea 

 enters the keel of the sternum, which is excavated to receive it, 



and where it forms one or more 

 coils before emerging to pass to 

 the lungs. This curious winding 

 is carried to an extreme in Grus 

 americana, the whooping crane, in 

 Avhich the windpipe is about as 

 long as the whole bird, and about 

 half of it — over two feet of it ! — 

 is coiled away in the breast-bone 

 (Fig. 99). The same thing occurs 

 in G. canadensis to a less extent 

 (Fig. 100). In a guinea-fowl, 

 Gutter acristata, a loop of the 

 trachea is received in a cup formed 

 by the apex of the clavicles. In 

 various birds, as some of the 

 curassows (Cracida'), the caper- 

 caillie (Tctrao urogallus), a goose, 

 Anseranas semipalmata, and the 

 female of the curious snipe, Rhjnduea australis, the trachea folds 

 between the pectoral muscles and the skin. 



The Larynx (the Gr. name, Xdpvy^, larugx) is the peculiarly 

 modified upper end of the trachea (Fig. 101, ^, and ^ to ^^). In 

 mammals it is a complicated voice-organ, containing the vocal chords 

 and other consonantal apparatus ; in birds the construction is 

 simpler, as the larynx merely modulates the sound already produced 

 in the lower end of the tube. It lies in the floor of the mouth, at 

 the root of the tongue, between the forks of the hyoid bone, resting 

 upon the urohyal. Besides its attachments of mucous and other 

 membrane, it is connected with the hyoid bone by a pair of thyro- 

 hyoid muscles (^S^), and usually with the rest of the trachea by 

 prolongations of the sterno- and clido-tracheales. It is usually a 

 small, simple, conical " mouthpiece " of the pipe {*, a), without the 



Fig. OS. — Bony labj'rintli at bottom of the 

 trachea of the male of Clangula islandiea, 

 seen from behind, nat. size. I)r. R. W. Shu- 

 feldt, U.S.A. 



